Embodiments of the subject matter disclosed herein correspond to reciprocating machine, such as compressors and more particularly, but not exclusively, hypercompressors and packing cups and packing cases for those machines.
It is known that hypercompressors are reciprocating machines where a fluid is converted to an extremely high pressure (for example up to 3500 bar) because of a plunger compressing the fluid into a chamber; generally they can be single- or multi-staged.
It is known in the state of the art to arrange a sealing and jacket around the plunger or more generally around a piston rod of a reciprocating machine, like compressor or similar.
Such jacket usually comprises a packing case that in turn comprises a plurality of packing cups.
Packing cups usually have a disc-like shape and they are provided with a hole in the centre through which the plunger or rod passes when it reciprocates; the packing cups are assembled aligned and side by side with each other.
Each packing cup comprises plunger sealing rings intended to provide a seal on the plunger or rod; such plunger sealing rings have to be lubricated in order to avoid frictions and wear against the plunger or rod; to this end the packing case is provided with ducts intended for the passage of the lubricant; lube ducts are therefore housed in the packing cups.
For example, with reference to a packing case comprising five packing cups, it is assembled with a first packing cup adjacent to a distribution cup (usually remotely from the compressor chamber) followed by a second, third, fourth and fifth successive packing cups. Usually a ring carrier and a pressure breaker cup, adjacent to the compressor chamber are provided adjacent to the fifth packing cup.
Lubrication, for example, provides to bring the lubricant to the second and fourth plunger sealing rings (placed between the first and the second packing cups and between the third and the fourth packing cups respectively) and to further lubricate the region between the fifth packing cup and the ring carrier.
To this end lube oil ducts passing through one or more of the packing cups are provided.
In details, with reference to the known art just described, the duct intended to bring the lubricant to the second plunger sealing ring comprises an initial portion that passes through the distribution cup, an intermediate portion that parallel—with respect to the plunger axis—passes through the first packing cup and an end portion radial—with respect to the plunger axis—ending in the region to be lubricated.
Similarly, the duct intended to bring the lubricant to the fourth plunger sealing ring comprises an initial portion that passes through the distribution cup, an intermediate portion that parallel—with respect to the plunger axis—passes through the first, the second and the third packing cups and an end portion—radial with respect to the plunger axis—ending in the region to be lubricated.
Still similarly, the duct intended to bring the lubricant between the fifth packing cup and the ring carrier comprises an initial portion that passes through the distribution cup, an intermediate portion that parallel—with respect to the plunger axis—passes through the first, the second, the third, the fourth and the fifth packing cups and an end portion—radial with respect to the plunger axis—ending in the region to be lubricated.
From this situation it results that each packing cup, depending on its position in the packing case, houses (or not) one or more parts of the intermediate portion of the different ducts: the fact of placing the several packing cups side by side in the assembled condition causes the parts of the duct intermediate portions to be joined till forming the complete ducts.
The duct intermediate portions are made as through holes passing from one face to the other one of the packing cup, while the duct end portions are made as radial grooves (with respect to the plunger axis) connected to the relevant duct intermediate portions and ending at the region to be lubricated.
For instance, in the example just described, the first packing cup is provided with three holes: each one is a part of the intermediate portion of the first, second, and third ducts respectively intended to bring the lubricant to the second and fourth plunger sealing ring and in the region between the fifth packing cup and the ring carrier respectively.
The second packing cup is on the contrary provided with two holes: each one is a part of the intermediate portion of the second and third ducts respectively intended to bring the lubricant to the fourth plunger sealing ring and in the region between the fifth packing cup and the ring carrier respectively; the second packing cup is further provided with a radial groove, which is the end portion of the first duct.
The third packing cup is provided with two holes: each one is a part of the intermediate portion of the second and third ducts respectively intended to bring the lubricant to the fourth plunger sealing ring and in the region between the fifth packing cup and the ring carrier respectively.
The fourth packing cup is on the contrary provided with one hole as a part of the intermediate portion of the third duct intended to bring the lubricant in the region between the fifth packing cup and the ring carrier; the fourth packing cup is further provided with a radial groove, which is the end portion of the second duct.
Finally the fifth packing cup is provided with one hole as a part of the intermediate portion of the third duct intended to bring the lubricant in the region between the fifth packing cup and the ring carrier which, on its turn, comprises a radial groove.
From such exemplary situation it is easy to understand how each packing cup is unique, meaning that, once its position inside the packing case is established, it has to comprise certain ducts and no other ones.
Therefore, from the above, a first drawback of the known solutions is clear, which leads to produce each packing cup in a different manner depending on its position in the packing case; from this derives the need of having a plurality of single (first, second, third etc) packing cups in stock if it is necessary to replace one of them for maintenance reasons.